Indoor air quality in the home plays a major role in your respiratory health, particularly if you suffer from asthma or allergies. Research by the American Lung Association has shown that a majority of Americans (87%) are not aware that the air inside of most American homes is more polluted than the air outside.

Fortunately, there are some concrete action steps you can take to improve your living space:

Increase ventilation. Use exhaust fans when cooking, showering, and using the dishwasher.

Make sure your clothes dryer is vented to the outdoors.

Maintain a comfortable temperature and low humidity.

Do not allow smoking in the house. Avoid using a wood-burning stove or fireplace. Make sure it is airtight if you do use one.

Avoid using perfumes or scented cleaning sprays. Use trigger sprays instead of aerosols.

Improve air filtration.

The Environmental Protection Agency (EPA) considers indoor air pollution to be one of the five most urgent environmental problems in the United States. Cases of asthma have increased 60% in the past two decades, and it is likely that some of this increase is due to indoor air problems. The most susceptible individuals are the elderly, the young, and those whose health is impaired, particularly those with a respiratory or immune system condition.

In order to avoid asthma and allergy symptoms, keep your indoor air as clean as you can by identifying and controlling the sources of airborne irritants in your home. There are three kinds of irritants:

Gases from wood products and other sources (e.g., radon, formaldehyde)

Increase ventilation

Proper ventilation in certain areas of the home is essential for improving your indoor air quality. An everyday task like cooking can produce odors, water vapor, and other potential irritants like grease and smoke. Avoid using standard window fans for ventilation, because they allow pollen and outdoor mold spores to enter the house. Use exhaust fans in the kitchen and bathroom to remove moisture and indoor pollutants.

One good type of exhaust fan is a properly sized range hood exhaust fan with an outlet to the outdoors. Also use an exhaust fan to the outdoors in the garage, particularly if the garage is attached to the house. This will prevent car fumes from entering the house. Weather stripping on the door leading from the garage to the house would also help to keep the exhaust gases out of the house. If you have any ductwork for a forced-air heating/air conditioning system in the garage, make sure it is well sealed.

If your home is always stuffy, consider a whole-house ventilation system apart from your existing forced-air heating and cooling system. A standard forced-air heating and cooling system pulls air from inside the home through one register or grate and forces the warmed or cooled air out of another. The heating and cooling system of an average U.S. home does not include a ventilation system that pulls in fresh air from outside.

Control Temperature and humidity

People with allergies or asthma need to monitor the temperature and humidity in the home. Air conditioning often helps, particularly because it allows you to keep the windows closed on high-pollen days and keeps mold growth and dust mites to a minimum. (Check our pollen forecast for your region.) A centralized heating and cooling system helps to maintain the same temperature and control humidity throughout the house. As a second choice, a single room, window air-conditioning unit can provide adequate cooling, which is particularly important in the bedroom. Be sure to clean the filters regularly.

Use a dehumidifier to keep the level of moisture in the house to a relative humidity of 35 - 50%. Keeping the house cool and dry helps reduce mold, dust mites, and cockroaches. However, this may be a difficult task depending on where you live. According to Dr. Elaine Gonsior, Director of the Allergy Clinic at Kansas State University, it is very difficult to get humidity levels below 50% in many areas of the United States, even with air conditioning and dehumidifying. "Levels as low as 35% can only be achieved in standard homes in cold, dry climates unless the insulation and ventilation are hi-tech, and that is beyond the reach of the average homeowner," Gonsior says.

Avoid smoke and combustion products

Secondhand tobacco smoke is a major asthma trigger. Young children are at the greatest risk because their lungs are still developing. Secondhand smoke exposure is associated with lower respiratory tract infections (like bronchitis and pneumonia), ear infections, increased severity and frequency of asthma episodes, and decreased lung function. Don't allow smoking in the house or in the car, particularly in the presence of a young child. If you decide to smoke, smoke outside.

If you burn candles, you may be releasing smoke, soot, and small amounts of toxic chemicals like benzene, lead, and mercury into the air. Make sure the wicks are short -- burning a long wick can result in a larger flame and produce more soot. Also, you may want to avoid using scented or slow-burning candles because they might contain toxic additives.

Wood-burning stoves and fireplaces also can be a source of smoke that trigger asthma or allergy symptoms. If you must use a wood burning stove or fireplace, use dried or cured wood instead of pressure-treated wood (fewer fumes are given off) and have your chimney or flue cleaned and inspected regularly. Other fuel-burning appliances, like gas ranges, oil furnaces, water heaters, and space heaters, release combustion by-products that can pollute indoor air significantly and trigger asthma symptoms in some people.

Have these appliances inspected and maintained regularly to identify leaks or damage. Backdrafting (downward air flow in a chimney) can allow soot or smoke to enter the living space. Ask a chimney specialist to check the air pressure inside and outside the chimney to prevent backdrafting. The optimal heating system for someone with allergies or asthma would limit exposure to the by-products of burning wood or fossil fuels. Heat pumps, electric baseboard heaters, geothermal heating, or sealed combustion heating are good examples.

Keep the house clean

Since many irritants can be trapped in dust, try to keep your house dust-free. Once a week, use a damp cloth to wipe all flat surfaces. Be careful with the cleaning agents you use. Some scented or aerosol sprays and other cleaners can be irritants for people with asthma and allergies. To be on the safe side, use trigger sprays and a face mask, and increase ventilation while cleaning to minimize your exposure to irritating chemicals.

Inspect the air ducts in your house. Sometimes dust and mold can accumulate in the ducts of your home's forced-air heating and cooling system, which may result in further dispersion of these allergens into the air. This can be a problem in homes with pets, or in areas of high humidity. Consider hiring a professional to examine or clean your ductwork.

Improve filtration

To improve your existing forced air heating/cooling system, consider installing an electrostatic filter. These filters, which work 3 - 4 times better than a standard foam filter, can be easily installed on your system to minimize small airborne particles that are potential allergens. An alternative to the electrostatic filter is the extended-surface air filter. This accordion-like filter, which is usually 2 - 6 inches thick, requires installation by a professional heating/cooling contractor. The extended-surface filter can last up to 2 years and can capture more airborne allergens than an electrostatic filter.

After taking these steps to remove obvious sources of indoor air pollution, consider purchasing an air cleaner to eliminate any airborne particles that remain. Air cleaners range in size, type, and efficiency. You can choose from an inexpensive, stand-alone, tabletop unit to more involved and expensive whole-house systems. The standard measure to rate the efficiency of an air cleaner is the Clean Air Delivery Rate (CADR), measured in cubic feet per minute. A higher CADR indicates greater ability for the air cleaner to return clean air to the room. Some models are designed with a higher CADR for one type of particle than another.

Desktop models are generally too small to be effective, but a stand-alone, single-room High Efficiency Particulate Accumulator (HEPA) air cleaner can help filter out airborne particles like smoke, dust mite allergens, and pet allergens. Electronic air cleaners (also called electrostatic precipitators) are quite efficient, but they release a small amount of ozone while they're running. In general, air cleaners do not remove irritating gases, such as radon, carbon monoxide, or formaldehyde. However, if they contain activated carbon (or similar material) they can remove some types of gases.